I checked Facebook this morning, bought a book on Amazon last week, and used Google throughout the day. My guess is that your experiences are similar. How have these technologies come to play such an integral role in our lives?
Digital technology allows market dominance because it makes capacity constraints irrelevant -- "a single producer with a website can, in principle, fill the needs of millions or even billions of customers." So argues the authors of the book "The Second Machine Age."
Brick-and-mortar businesses incur significant costs in expanding and maintaining a large footprint. Facebook can serve a good portion of the planet with ease. The next participant adds nothing much to Facebook's expenses. Technology allows Facebook to operate with under 20,000 employees; General Motors has 200,000. (I looked it up on Google.)